digi01 said:
First of all provide protection diodes as is suggested on the LM317 datasheet.
Second, the output capacitors should be smaller, at least on the 338. Look at Carlos findings on how the 3886 sounded when the regulator used smaller caps. He put a film cap at the 338 output and a small 'lytic by the 3886.
If you are going to design a pcb, also provide pads for a resistor instead of a trimpot. After you set the voltage it might be better to use a fixed resistor.
Carlos
Hi Carlos,
as stated in the LT108x datasheet, those ICs need a minimum capacitance at the output to ensure stability. It's good to provide an adjust pin capacitor too (as Digi has done), but this increases the required output cap size even further.
I think the circuit is safe with the 220uF for the LT108x. As for the LM388, nobody forces one to put a big cap in. But it's wise to provide the board space.
Sebastian.
as stated in the LT108x datasheet, those ICs need a minimum capacitance at the output to ensure stability. It's good to provide an adjust pin capacitor too (as Digi has done), but this increases the required output cap size even further.
I think the circuit is safe with the 220uF for the LT108x. As for the LM388, nobody forces one to put a big cap in. But it's wise to provide the board space.
Sebastian.
sek said:
There are very few comments to get use info about the LT108x chips on this forum. So I wouldn't risk going too high without trying and listening. Adjust pin cap is certainly good, and it's there where you can go high, not at the output. You will need protection diodes there, though.
In fact I think diode protection should be used between: input/output, adjust pin to to output, and output ground. Though the latter is not necessary if output cap is small.
Providing space is nice if you have it, particularly because you can try film caps if capacity is small and go for better quality. On the 338 you should try first what people used here and seemed to work better: small caps. Then see what works better for you.
Carlos E. Martinez
main components mounting details:
U ,regulator chip
the board can mounting to-220 or to-3p types.
DIODE
each one,the foot distance is 400mil ,10.16mm.
C2
foot distance 300mil/400mil,7.62mm/10.16mm.
radius max=16mm
leg holes 2mm
can mounting common audio quality caps.
Rtrim
it is for setting the output voltage, the range is from 20V to 32V.
the board pads can moungting a resistor or a trimpot.as Carlos motions,after you set the voltage it might be better to use a fixed resistor.
Hi dig1-
Please pardon my ignorance, but this circuit is for one side of the pwr rail correct? From the schematic it shows -V and grnd. Is there another circuit for the +V and grnd?
Also, is there a circuit for a single transformer and Bridge rectifier for both rails? I have use for both Ultimate pwr supplies with separate transformers and standard power supplies with a single transformer and BR.
Thanks, Troy
Please pardon my ignorance, but this circuit is for one side of the pwr rail correct? From the schematic it shows -V and grnd. Is there another circuit for the +V and grnd?
Also, is there a circuit for a single transformer and Bridge rectifier for both rails? I have use for both Ultimate pwr supplies with separate transformers and standard power supplies with a single transformer and BR.
Thanks, Troy
digi01 said:
I'm sorry to tell you, but with those output caps the amp will sound very bad.
Look at my schematic above, check the difference in value for the output cap, after the reg.
And you need a small cap before the reg too.
It's all there, I've tested it, I listened, I changed, listened again...
I see some schematics of this PSU on this forum that will make the GC sound worse than unregulated.
I know, my thread is still closed...
thank you carlosThis is two respects of a question.
my PCB design is to hold and accomodate different components while fully utilize the board room.as Sebastian mentiond.
the output caps C5* and C4,I just leave the enough room on the board.you can free play it when LM338 or LT1083 be used.
the same in value and room for the C2 .
H.B
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